Abstract: A method of controlling a combustion turbine engine, wherein the engine includes: a fuel line including a heat exchange portion; a heating value meter; a cold leg bypass comprising an alternate fuel line that bypasses the heat exchange portion, the cold leg bypass being connected to the fuel line at an upstream fork and at a fuel mixing junction, the fuel mixing junction being positioned such that a length of fuel line between it and the inlet to the combustor is short; and valves for controlling the amount of fuel being directed through the heat exchange portion; the method comprising: measuring the heating value of the fuel; determining a target fuel temperature range based on the heating value and a target Modified Wobbe Index range; and controlling the fuel that bypasses the heat exchange portion such that the temperature of the fuel is within the target temperature range.